The present invention relates to a vehicle seat belt retractor and more particularly, to such a retractor which may be used either as an inertia-operated locking retractor or an automatic locking retractor (ALR retractor).
When the seat belt retractor is in the inertia-operated mode, the seat belt is unrestrained against protraction by the seat occupant until the inertia member moves at the time of a sudden deceleration to actuate a locking pawl or bar into locking engagement with ratchet wheels on a retractor reel. The reel is locked and no further belt protraction is possible. Thus, the retractor is locked only at the time of an inertia event of sufficient magnitude to cause the locking. On the other hand, the automatic locking retractor is normally locked when positioned about an object or a person on a seat such that no further belt protraction is possible. The usual operation in an ALR retractor is that the seat occupant pulls the belt about one's self and inserts the tip or tongue plate into the seat buckle and releases the grip on the tip whereupon the seat belt is retracted slightly as the belt becomes cinched tight about the occupant. This sequence of actions cause the lock bar to be actuated into locking engagement with the ratchet wheels and to remain so locked until the tip is unbuckled and the belt is allowed to rewind onto the reel.
In addition to protection of seat occupants, the ALR retractor is especially useful to lock baby seats or objects against shifting on the vehicle seats. More specifically, the belt is pulled about the baby seat or an object on the seat and buckled and the belt rewinds slightly to cinch tightly; then the retractor is locked automatically and remains locked against further belt protraction until the seat belt is unbuckled. Thus, the baby seat, object or person is continually cinched tightly with the automatic seat belt retractor and hence, is not able to shift or otherwise it might move as if it were being held by an inertia retractor or in the inertia retractor mode of a convertible retractor.
There is a particular interest today in having seat belt retractors, particularly for rear seats of automobiles, to be convertible between an inertia-locking mode and an ALR mode. When a person is in the rear seat, the person will usually prefer the inertia-operated mode allowing the person freedom of movement until the inertia member is operated to lock the retractor. When a baby seat is placed on the rear seat, the retractor will be converted to the ALR mode to lock the retractor and the baby seat in position initially and then to remain in this locked, cinched position so that the baby seat will not shift on the rear seat.
Convertible seat belt retractors are well known in the art, e.g., U.S. Pat. Nos. 4,552,319; 4,566,649; 4,573,646; 4,327,882; 4,817,885; 4,767,082 and 4,519,132. In these patents, the conversion is made from the inertia mode to the ALR mode by pulling the belt from the reel for a predetermined length of belt, this usually being substantially all of the belt on the reel. A belt or spool diameter sensor determines when the belt is unwound sufficiently to actuate the ALR mechanism to become effective and to render the inertia mechanism ineffective. Various constructions of retractors have been made to be convertible; but often the designs are complex and inexpensive or not easily operated by user between modes. Size is another factor, since the convertible seat belt retractor may be so large that it cannot be used relatively interchangeable with the usual inertia-operated retractor, which may be of a substantially smaller size.